> On 04.01.2019|KW1, at 15:22, Frank Sheeran <fshee...@gmail.com> wrote:
> 
> Thank you Nigel, RB-J, Steffan, and Neil.


You’re welcome!
> 
>  
> 
> i suspect that those tone wheel waveforms are close to sinusoidal.
> 
> Early models were.  Starting I think around '53 with the B-3, C-3 and A1xx 
> series (A100 etc.) they were a bit brighter, and the foot pedals were FAR 
> brighter.


Actually, only the wheels #1 -#13 have a sort of complex waveform. But the 3 
series have a slight level slope, the higher frequencies are a bit louder. This 
was a kind of emphasis, which in conjunction with a de-emphasis filter in the 
pre-amp reduced the key click a bit. As a penalty, the harmonic distortion of 
the higher tone wheels is a bit higher. 

> 
> A social network acquaintance supplied me the recording.  I'm not sure where 
> they tapped in to get it.  What it DOES have--and I'm glad of it--is the 
> leakage from the neighboring disk.  The disks are basically all in little 
> compartments of two disks, 4 octaves apart,

There are some wheels with 192 teeth, so the distance is not 4 octaves but an 
extra quint.


> and each disk is picked up by the other's pickup to some extent.  It's 
> absolutely audible, maybe -36dB down or something.

This can be pretty enervating, depending on the organ. Later models had extra 
networks to remove the “sub-harmonic”. 


>  
> 
> The tonewheels are intended to be perfectly sinusoidal, though their mass
> stamping does introduce various differences. The exception is the lowest
> octave of certain models, B3 included, made at certain times, as described
> here:
> 
> My understanding is that the first Hammonds up to the but not including the 
> B-3/C-3/A1xx models, were nearly sinusoidal, but after that they were 
> brightened considerably and that's what I'm seeing in my recording.

This might be introduced by the recording. The Hammond organ is a current 
mixer, the output of the tone wheel and the subsequent filter present on tone 
wheels #49 - #91 runs into matching transformer with a primary resistance < 1 
ohm via mixing resistors , which are  between 30 -100 ohm IIRC, typically 50 
ohm.

>  
> 
> http://www.dairiki.org/HammondWiki/ToneWheel 
> <http://www.dairiki.org/HammondWiki/ToneWheel>
> 
> Given the intent of the tonewheel, I wouldn't bother with this particular
> experiment at all if I were trying to recreate a B3.  But then, I wouldn't do 
> any foldback either.


The foldback in the lowest octave was necessary to circumvent the missing 
sinusoidal wheels #1- #13, which had complex wave forms now. 
The foldback in the upper octaves was always there and is necessary to achieve 
the typical sound of an organ with all stops pulled out. 


> 
> Hey, if you don't want an actual Hammond, that's why I wrote the entire soft 
> synth in the first place!  :-D
> 
> The main reason I'm doing this patch is as a case study showing my soft synth 
> can emulate a real Hammond

The Synclavier was claiming that, too. It worked to a certain extent. 

> (and Leslie)

That’s the hard thing, since the Leslie defined the sound much more than the 
organ itself. 


> warts and all, to a very deep level, and showing how one would go about it.
> 
> But it's also well-known that every tonewheel
> organ has its own character due to being a very complex electro-mechanical
> device, so I suppose I might try this analysis if I were attempting to
> create a framework for creating such differenced organs.
> 
> The more modern "clonewheel" organs do let you simulate each wheel's 
> harmonics individually, etc.  In fact I should go look at a Hammond XK-5 just 
> to see if my research is similar to their default settings.

You can adjust the levels but not the harmonics themselves. But even that works 
well. 

>  
> It'd be interesting if a clonewheel manufacturer had an automated service 
> whereby you upload a recording as I requested of my organ acquaintance, then 
> let you download a patch that matched that exact organ.

Since most organ owners don’t have the knowledge nor the equipment how to 
create the recording, I doubt that this might be a great business model. 
Although it is somehow similar to the Kemper amp business model, I’d would 
assume, that most buyers of the Kemper amp are fine with the models supplied 
and shared over the internet. 

Best,

Steffan 


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